I. Field of the Invention
This invention relates generally to communications. More specifically, the invention relates to synchronization in a wireless communication system.
II. Description of the Related Art
The wireless medium is becoming one of the predominate means by which voice information and digital data are transferred in modern society. In wireless communication systems, it is common that a plurality of remote units communicate with a single hub station. In order to combat the harsh wireless environment while providing multiple access to a plurality of remote units, modulation schemes which provide efficient data transfer, as well as user channelization, have been developed. In general, these modulation schemes operate most efficiently when the signal from each remote unit arrives at the hub station with a synchronized timing. For example, in a time division multiple access (TDMA) system, each remote unit is assigned a time slot in which to send its data. If the timing of one remote unit is misaligned with respect to the timing from another remote unit, the transmission from one remote unit may overlap in time the transmission of another, thereby, yielding both transmissions unusable. In a typical code division multiple access (CDMA) system, the remote unit signals are distinguished through the use of nearly orthogonal pseudo random codes. If the transmission from one remote unit becomes misaligned with the transmission from another remote unit, the orthogonal nature of the pseudo random codes is degraded and the signals may significantly interfere with one another. Therefore, in both of these types of systems, it is necessary that the remote units operate synchronously with one another.
Therefore, it is desirable to provide an effective method for synchronizing plurality of remote units communicating with a common hub station.